Explanalion of the CzUlcle of Leaves. 165 



they contain, and how many various juices are thus produced to 

 the plants ; for it is by no means to be conceived that one sort 

 of hair altvays brings the same juice. I liave proved how very 

 differently this is managed in seeds, by seeing and detecting the 

 same hairs bringing not oidvvarious coloured juice?, but changes 

 of gases, known to be so by the alteration of tints of the air- 

 bubbles : at one time the vessels would be full, then chnn^iug ; 

 every day produce a new ingredient, t doubt not it is the same 

 in all other plants which receive moisture and support from the 

 leaves. 



Evergreens receive no moisture whatever from the atmosphere. 

 Besides the impervious skin which forms their outward cuticles 

 both above and below, they are so guarded over the pabulum 

 by a thin layer of bark juices, and bladders of inflammable air, 

 that no moisture can apjiroach them in that direction. They 

 have five upper cuticles and three under ones, all so closely 

 pressed together, as apparently to form but one : those that 

 have scented leaves have in the second cuticle bladders of an 

 oily compound : this evidently enters from the atmosphere, and 

 it is thus all leaves are scented, the perfume being kept perfectly 

 separate from the rest of the juices of the plant. The scent would 

 be strong indeed if it could be taken thus : but this is impossible, 

 and by distillation we again separate it from the general liquid, 

 with which it gets mixed in drawing it from the plant. It is 

 however greatly to be regretted that we cannot contrive at once 

 to draw the several liquids from a plant without this assemblage, 

 as it would give a much clearer view of the subject. It will be 

 asked. As these leaves have 710 hairs, QnA no collecting cuticle, 

 how they can receive the oil and all the various juices they must 

 require to form the compounds and gases necessary to theirhealth 

 and vigour? I know but of three means: the edoes of the 

 leaver ; the large open points common to all evergreens ; and 

 the top of the gatherer ; for in these leaves it is only the under 

 part that draws up ; the other is studded with pore's formed in 

 a curiou"- manner within-, and as this formation is only to be 

 discovc red in these leaves, I take it to be some indemnification 

 for the very few hairs they possess. It must however be noticed, 

 that, like alin.')st all other plants, when first shooting they have 

 many hairs. The extreme shining of the upper cuticle is caused 

 by the glutinous matter which fills up like oil the network of 

 the exterior one, and renders it perfectly lucid ; and it is this 

 hard and stiff skin, and the bladders of infiammable air, which 

 caase it to explode when placed in the fire ; and it is this glu- 

 tinous cuticle which protects it from the cold of the winter; and 

 in proportion as these glazed skins are (uaiiyin number, so much 

 more will they endure the frosts of the winter. This is the 



L 3 reason 



